CD19 and Parkinson disease: In our study, we also found that the percentage of CD19+ B cells among PBMCs was significantly lower in PD patients than in HCs [5.35% (4.13–9.38%), 95%CI (4.10, 7.01%) vs. 8.68% (5.61–12.93%), 95%CI(6.49, 11.80%), P = 0.014, Figure 2D].